The present invention discloses a device for the tight connection of two parts, e.g. pipes, each part having a flange. The device has flange locking means, in order to compress a gasket between the two parts.
A tight connection device of this type is disclosed e.g. by French Patent Application No. 8,101,250, filed on Jan. 23rd 1981 in the name of the Commissariat a l'Energie Atomique and entitled "Elastic locking tightening device". This device has locking or tightening means of the screw-nut type, which join the parts to one another, in order to compress a gasket between them.
In some industrial applications, in order to ensure a connection between pipes with high sealing and reliability performance levels, the use of couplings having a static gasket requiring high tightening forces, such as a metal gasket, is required. However, a tightening or locking device of the type described above cannot ensure such a high tightening force or stress.
In addition, in order to simplify or automate tightening, it is often necessary to use a mechanical means of the hydraulic or electric jack type, in order to lock the assembly and crush the gasket in accordance with the assembly specifications. This makes it possible to simplify the closing of the locking or tightening system, because no stress is exerted thereon. For example, if this tightening system is a nut and bolt system, the bolts can be manually screwed. This is of particular interest in the case when there is no space to introduce a locking member, such as a locking key. In this case, before eliminating the action of the jack, it is necessary by means of an appropriate system to prestress the assembly, in order to keep it correctly secured. This is brought about by tensioning the locking means, otherwise the elastic reaction of the gasket would bring about the load relief thereof.
In order to simulate this stress maintaining problem, it is merely necessary to form the two elastic elements constituted by the gasket and the locking system by two springs A and B.
FIG. 1a shows an elastic system with two springs A and B. Spring A provides the elasticity of the gasket and spring B that of the locking system. Spring A is compressed by exerting a force F on plate p.
Plate q is locked on spindle r, e.g. by means of a screw v, so that spring B is not compressed. Thus, on taking the example of a nut and bolt system, if the bolts are manually tightened, it is readily apparent that they cannot be tightly locked.
On releasing the force F exerted e.g. by a jack, the spring reaction on plate p, which was previously balanced by the action of the jack, is transmitted to spring B, which is compressed. The point of equilibrium is at F.sub.0 (see FIG. 1b). Spring B represents the elasticity of the nut and bolt system. Spring A is relaxed by value .delta. and spring B compressed by the same value .delta.. Thus, the gasket whose elasticity is represented by spring A has loosened. However, in order to correctly ensure the sealing, it is necessary for the gasket to be adequately compressed.
In order to obviate this gasket load relief phenomenon, it is necessary, in the manner indicated hereinbefore, to prestress the tightening system by tensioning the same. However, this is not possible in all cases, particularly due to lack of space.